To meet the demand for wireless data traffic having increased since deployment of 4th generation (4G) communication systems, efforts have been made to develop an improved 5th) generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post Long Term Evolution (LTE) System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid frequency shift keying (FSK) and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
To obtain a transmission gain in an FD-MIMO system, a terminal needs to recognize accurate channel information by each antenna of a base station providing a service to the terminal. The base station may allocate a Channel State Information (CSI)-Reference Signal (RS) by each antenna to a resource element in order to transmit the accurate channel information by each antenna of the base station to the terminal. The terminal may receive the CSI-RS by each antenna of the base station.
FIG. 1 illustrates an example of reference signal allocation by a transmitting antenna in a wireless communication system. Referring to FIG. 1, in an FD-MIMO system, when reference signals for antennas are allocated to resource elements (REs) corresponding to the increased number of antennas, a problem of a reduction in frequency/time resources available for data transmission occurs. For example, when 64 resource elements are available and the base station uses 16 transmitting antennas 101, if the base station allocates reference signals for the respective 16 transmitting antennas to separate resource elements among the 64 resource elements, the number of frequency/time resources for data transmission is reduced by those for the 16 reference signals. Further, when the base station uses 64 transmitting antennas 103, if the base station allocates reference signals for the respective 64 transmitting antennas to the separate 64 resource elements, no frequency/time resource may be left for data transmission.
As described above, when there is a plurality of transmitting antennas, a reference signal for each antenna needs to occupy an exclusive resource. Accordingly, when the base station allocates a reference signal for each of the plurality of antennas of the base station to a resource, resources for data transmission may be insufficient.